Wireless tissue dissector

ABSTRACT

A tissue dissector includes a handle assembly including an actuator, a head portion including a blade member defining an aperture configured to receive tissue therethrough, and a lighting assembly configured to provide lighting to the aperture of the blade member. The blade member is operatively coupled with the actuator for rotation about the aperture.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of and priority to U.S. Provisional Patent Application Ser. No. 62/854,448 filed May 30, 2019, the entire disclosure of which is incorporated by reference herein.

BACKGROUND Technical Field

The present disclosure relates generally to the field of tissue cutting and removal. In particular, the present disclosure relates to a wireless tissue dissector.

Background of Related Art

Surgical cutting instruments in which an elongate inner member is rotated within an elongate, tubular outer member are utilized in surgical procedures where access to the surgical site is gained via a narrow portal or passage. Typically, the tubular outer member includes a distal end with an opening defining a cutting port or window and the inner member includes a distal end with a cutting tip for engaging bodily tissue via the opening. Proximal ends of the inner and outer members commonly include hubs which attach to a handpiece having a motor for rotating the inner member relative to the outer member. The distal end of the inner member may have various configurations dependent upon the surgical procedure to be performed, with the opening in the distal end of the outer member being suitably configured to cooperate with the particular configuration of the distal end of the inner member to cut, resect, and/or abrade tissue. Often the inner member is tubular so that the loose tissue resulting from a cutting, resecting, and/or abrading procedure can be aspirated through the hollow lumen of the inner member.

SUMMARY

As used herein, the term “distal” refers to the portion that is described which is farther from a user, while the term “proximal” refers to the portion that is described which is closer to a user. Further, to the extent consistent, any or all of the aspects described herein may be used in conjunction with any or all of the other aspects described herein.

In accordance with an aspect of the present disclosure, a tissue dissector includes a handle assembly including an actuator, a head portion including a blade member defining an aperture configured to receive tissue therethrough, and a lighting assembly configured to provide lighting to the aperture of the blade member. The blade member is operatively coupled with the actuator for rotation about the aperture.

In an aspect, the aperture of the blade member may be tapered along a longitudinal axis thereof.

In another aspect, the blade member may include an edge portion configured to cut tissue.

In another aspect, the lighting assembly may include a plurality of light emitting diodes circumferentially arranged about the aperture of the blade member.

In yet another aspect, the handle assembly may further include a removable battery pack to supply power to the actuator and the lighting assembly.

In an aspect, the head portion may include first and second sides opposing each other. The blade member may extend from the first side.

In another aspect, the lighting assembly may be disposed on the second side of the head portion.

In another aspect of the present disclosure, a tissue dissector includes a handle assembly including an actuator, a head portion including a blade member defining an aperture configured to receive tissue therethrough, and a lighting assembly. The blade member is operatively coupled with the actuator for rotation about the aperture to cut tissue. The lighting assembly includes a circular rim disposed on the head portion and a window assembly rotatably supported on the circular rim. The circular rim has a light source. The window assembly includes a first window having a first opacity. The first window is in registration with the light source.

In an aspect, the window assembly may further include a second window having a second opacity different from the first opacity.

In another aspect, the window assembly may be removably attached to the circular rim.

In yet another aspect, the circular rim may support a plurality of light sources, and the window assembly may include a plurality of windows. At least two windows of the plurality of windows may have a different opacity.

In yet another aspect, the plurality of windows may include opacities of 100%, 75%, 50%, and 25%.

In still yet another aspect, the plurality of windows may be arranged in a repeating sequence of opacity such that the plurality of light sources is in registration with the plurality of windows having the same opacity.

In an aspect, the head portion may include indicia indicating different opacity and the window assembly may include an indicator selectively positionable on the indicia to selectively align the light sources to the windows having a predetermined opacity.

In another aspect, the head portion may further include a pair of stops to limit rotation of the window assembly such that the light sources are in registration with the windows having the same opacity.

In an aspect, a longitudinal axis defined by the aperture of the blade member may be substantially orthogonal to a longitudinal axis defined by the handle assembly.

In another aspect, the head portion and the indicator may include mating configurations for alignment of the indicator and the indicia.

In yet another aspect, the lighting assembly may include a plurality of light sources. At least first and second light sources of the plurality of light sources may diametrically oppose each other.

BRIEF DESCRIPTION OF THE DRAWINGS

Various aspects and features of the present disclosure are described hereinbelow with reference to the drawings wherein like numerals designate identical or corresponding elements in each of the several views and:

FIG. 1 is a perspective view of a tissue dissector in accordance with the present disclosure;

FIG. 2 is a bottom perspective view of the tissue dissector of FIG. 1;

FIG. 3 is a bottom perspective view of the tissue dissector of FIG. 2 with a bottom housing half removed;

FIG. 4 is a perspective view of the tissue dissector of FIG. 1 with parts of a blade assembly separated;

FIG. 5 is another bottom perspective view of the tissue dissector of FIG. 1 with a bottom housing half removed;

FIG. 6 is an enlarged perspective view of the area of detail of FIG. 4;

FIG. 7 is a perspective view of a blade gear of the tissue dissector of FIG. 1;

FIG. 8 is a cross-sectional view of the tissue dissector taken along section line 8-8 of FIG. 1;

FIG. 9 is a bottom perspective view of another tissue dissector with a bottom housing half shown in phantom in accordance with the present disclosure;

FIG. 10 is a top view of the tissue dissector of FIG. 9 with a top housing half removed;

FIG. 11 is a perspective view of another tissue dissector in accordance with the present disclosure;

FIG. 12 is a partial perspective view of the tissue dissector of FIG. 11 with a window assembly separated;

FIG. 13 is a partial side cross-sectional view of the tissue dissector of FIG. 11;

FIG. 14 is a side cross-sectional view of the window assembly of FIG. 12;

FIG. 15 is a partially enlarged side cross-sectional view of a dissector head portion of the tissue dissector of FIG. 11 taken along section line 15-15 of FIG. 12;

FIG. 16 is a side cross-sectional view of the area of detail of FIG. 13;

FIG. 17 is a perspective view of a window assembly configured for use with a tissue dissector in accordance with the present disclosure;

FIG. 18 is a perspective view of the area of detail of FIG. 17; and

FIG. 19 is a perspective view of the area of detail of FIG. 17 illustrating rotation of the window assembly.

DETAILED DESCRIPTION

Embodiments of the present disclosure are described in detail with reference to the drawings, in which like reference numerals designate identical or corresponding elements in each of the several views.

With reference to FIGS. 1 and 2, there is provided a tissue dissector 100 for extracting tissue from a patient. The tissue dissector 100 includes housing halves 102, 104 configured to support a blade assembly 250 (FIG. 3) and an actuation assembly 410. The tissue dissector 100 includes a dissector head portion 200 including the blade assembly 250 (FIG. 3), and a handle portion 400 including the actuation assembly 410. In particular, the dissector head portion 200 includes an annular body 210 extending from the handle portion 400. The annular body 210 defines an aperture 201 configured to receive tissue therethrough. For example, the annular body 210 may be tapered to facilitate extraction of tissue from the surgical site through the dissector head portion 200. The handle portion 400 is ergonomically designed to be gripped by a clinician such that the clinician may easily access actuation buttons 430 to actuate the actuation assembly 410. Further, the dissector head portion 200 and handle portion 400 cooperate to define a common longitudinal axis that is disposed at an angle relative to a central axis defined through aperture 201. The angle may be, in embodiments, 90 degrees (such that the axes are perpendicular). In other embodiments, the angle may be from about 45 degrees to about 90 degrees, in other embodiments from about 60 degrees to about 90 degrees, and in still other embodiments, from about 75 degrees to about 90 degrees. In this manner, tissue is extracted from the surgical site through the tissue dissector at an angle, e.g., 90 degrees or an angle from about 45 degrees to about 90 degrees, relative to the longitudinal axis defined by the dissector head portion 200 and handle portion 400.

Tissue dissector 100 may be configured as a single-use device that is discarded after use or sent to a manufacturer for reprocessing, a reusable device capable of being cleaned and/or sterilized for repeated use by the end-user, or a partially-single-use, partially-reusable device. With respect to partially-single-use, partially-reusable configurations, the handle portion 400 may be configured as a cleanable/sterilizable, reusable component, while the dissector head portion 200 is configured as a single-use, disposable/reprocessable component. Under such a configuration, the dissector head portion 200 is configured to releasably engage the handle portion 400 to facilitate disposal/reprocessing of any single-use components and cleaning and/or sterilization of any reusable components. Further, enabling releasable engagement of the dissector head portion 200 with the handle portion 400 allows for use of different dissector head portions 200 with the handle portion 400.

With reference now to FIGS. 3 and 4, the dissector head portion 200 includes the annular body 210 (FIG. 1) configured to support the blade assembly 250. The blade assembly 250 includes a blade member 220 including a support portion 222, a blade portion 224 having e.g., a frusto-conical, shape, and a blade edge 226 configured to cut tissue. In particular, the blade member 220 defines an opening 221 in communication (and axial alignment) with the aperture 201 (FIG. 2) of the dissector head portion 200 and is configured to receive tissue therethrough. The blade assembly 250 further includes a blade gear 230 coupled with the blade member 220 for concomitant rotation therewith. In particular, the blade member 220 may be concentrically secured to the blade gear 230 via, e.g., adhesive, ultrasonic welding or a plurality of screws 228. In this manner, the blade gear 230 operatively couples the blade member 220 to a motor 420 of the actuation assembly 410. The blade gear 230 includes a coupling portion 232 configured to engage the support portion 222 of the blade member 220 such that the blade portion 224 extends away, e.g., distally, from the blade gear 230. In addition, the blade gear 230 defines an opening 231 in communication with the opening 221 of the blade member 220. The blade gear 230 further includes a plurality of teeth 236 circumferentially arranged around the blade gear 230 and disposed radially outward of the coupling portion 232. In this manner, the support portion 222 of the blade member 220 is disposed radially inward of the plurality of teeth 236. The plurality of teeth 236 is configured to operatively engage a plurality of teeth 436 of a transmission gear 418 supported on an output shaft 422 of the motor 420 of the actuation assembly 410. In this manner, rotational output of the motor 420 is imparted via the transmission gear 418 to the blade gear 230, which, in turn, causes rotation of the blade member 220.

With particular reference to FIG. 4, the blade gear 230 is rotatably supported in the annular body 210. In particular, the annular body 210 includes inner and outer walls 212, 214 that are concentrically disposed and configured to support a plurality of axial bearings 218. The plurality of axial bearings 218 is circumferentially arranged about the aperture 201 defined in the annular body 210. In particular, each axial bearing 218 is supported between the inner and outer walls 212, 214 and is rotatably supported within a circumferential groove 216 defined between the inner and outer walls 212, 214. In this manner, the plurality of axial bearing 218 enable rotation of the blade gear 230 supported thereon.

With reference now to FIGS. 5 and 6, each axial bearing 218 includes a pin 218 b supported in bores 212 a, 214 a defined in the respective inner and outer walls 212, 214, and a bearing sleeve 218 a rotatably supported on the pin 218 b. With reference now to FIG. 7, the blade gear 230 further includes a bearing surface 234 configured to engage the plurality of axial bearings 218. In particular, the bearing surface 234 may be raised from, e.g., a plane, defined by the plurality of teeth 236 such that the bearing surface 234 is at least partially disposed within the groove 216 (FIG. 4) defined between the inner and outer walls 212, 214 to guide rotation of the blade gear 230.

With reference to FIG. 8, in order to further facilitate stability and/or rotation of the blade member 220, the annular body 210 may include additional bearings in various orientations. For example, a second bearing 219 may be provided. The second bearing 219 may be configured to engage the blade gear 230 on the side thereof where blade gear 230 engages the blade member 220. Under such a configuration, the blade gear 230 is supported between the axial bearings 218 and the second bearing 219. For example, the second bearing 219 may be disposed substantially parallel to a longitudinal axis “X-X” defined through the aperture 201. In order to further enhance stability of rotation of the blade assembly 250 (FIG. 3), the plurality of axial bearings 218 may be in registration with a plurality of second bearings 219. Additionally, the annular body 210 may further include a third bearing 217 configured to engage an outer surface of the blade portion 224 (FIG. 4) of the blade member 220 to facilitate rotation of the blade member 220. In particular, the third bearing 217 may be disposed at an acute angle relative to the axis “X-X”. In order to enhance stability of the rotation of the blade member 220, a plurality of third bearings 217 may be provided about the blade member 220. It is contemplated that the tissue dissector 100 may include a control unit 700 (FIG. 3), e.g., a printed circuit board, to provide control functionality to the tissue dissector 100. It is further contemplated that handle portion 400 may include a battery pack 500 to supply power to the motor 420 and printed circuit board 700, although a cable (not shown) configured to connect to an external power source, e.g., standard electrical outlet, surgical generator, etc., is also contemplated. Under such a configuration, the tissue dissector 100 facilitates extraction of tissue by providing the aperture 201 having sufficient opening for tissue and a rotating blade edge 226 to cut tissue as it passes therethrough.

In use, the tissue dissector 100 is positioned with the dissector head portion 200 externally adjacent or partially extending into an opening, e.g., surgically created opening or naturally occurring orifice, providing access to an internal body cavity or organ. It is contemplated that the tissue dissector 100 may be used in conjunction with an access device, e.g., retractor, access port, or wound protector (not shown), in which case the dissector head portion 200 is positioned proximally adjacent or inserted partially through the access device anchored within the access opening at the surgical site. Once the dissector head portion 200 is positioned in the above manner, tissue dissector 100 is activated. The clinician may actuate the motor 420 by pushing an actuation button 430 (FIG. 1). Rotation of the output shaft 422 of the motor 420 rotates the blade member 220. In this manner, the clinician may cut and extract tissue by pulling the tissue up through aperture 201. The tissue dissector 100 may be utilized until the desired tissue is removed from the internal body cavity or organ. Once the desired tissue is removed, the tissue dissector 100 may be deactivated and removed from the surgical site. Thereafter, the tissue dissector 100 may be discarded, prepared for subsequent use, or sent for reprocessing.

With reference to FIGS. 9 and 10, there is provided a tissue dissector 1100 in accordance with another embodiment of the present disclosure. The tissue dissector 1100 is similar to the tissue dissector 100 and thus will only be discussed herein to the extent necessary to identify differences in construction and operation thereof. The tissue dissector 1100 includes an actuation assembly 1410 including a motor 420, a motor pulley 1418 operatively coupled with the motor 420, and a tensioner assembly 1450. The output shaft 422 of the motor 420 supports the motor pulley 1418 for concomitant rotation therewith. The blade member 220 of the blade assembly 1250 is secured with a blade pulley 1230 for concomitant rotation therewith. The blade pulley 1230 is operatively coupled with the motor pulley 1418 by a belt 1240. The belt 1240 further extends through the tensioner assembly 1450 having a biasing member 1452 configured to maintain desired tension in the belt 1240 by removing any slack in the belt 1240. Under such a configuration, actuation of the motor 420 drives the belt 1240, which, in turn, drives the blade pulley 1230. In this manner, the blade member 220 is rotated to cut tissue. The actuation assembly 1410 may protect the motor 420 in case of excess amount of torque, by causing belt slippage and inhibiting stalling of the motor 420. Further, such a configuration requires less precision and system alignment than a system that uses a gear assembly, which, in turn, requires, e.g., fewer friction reduction mechanisms. It is contemplated that the tissue dissector 1100 may include the battery pack 500 to supply power to the motor 420 and a printed circuit board 700 to control actuation of the motor 420 and supply of power from the battery pack 500. Use and operation of the tissue dissector 1100 is substantially identical to those of the tissue dissector 100, and thus, will be not be described herein.

With reference now to FIGS. 11-13, there is provided a tissue dissector 2100 in accordance with another embodiment of the present disclosure. In the interest of brevity, portions of the tissue dissector 2100 substantially identical to the portions of the tissue dissectors 100, 1100 will not be described herein to avoid obscuring the present disclosure in unnecessary detail. The tissue dissector 2100 includes a handle portion 2400 and a dissector head portion 2200 attached to the handle portion 2400. The dissector head portion 2200 includes a lighting assembly 2700 including a plurality of light sources 2702 such as, e.g., light emitting diodes (LED), and a window assembly 2800 having a plurality of windows 2802. The lighting assembly 2700 improves visibility of the surgical site and/or tissue, and thus, may improve safety of the patient, increase cutting efficiency, and reduce extraction time of tissue.

With particular reference to FIG. 12, the lighting assembly 2700 may include a plurality of lights sources 2702 circumferentially arranged about a longitudinal axis “Y-Y” (FIG. 13) extending through an aperture 2230 (FIG. 13) defined by the dissector head portion 2200. For example, the lighting assembly 2700 may include a plurality of pairs of diametrically opposing light sources 2702. The dissector head portion 2200 includes a protruding lip 2708 supporting the plurality of light sources 2702. The protruding lip 2708 is configured to rotatably support the window assembly 2800 having the plurality of windows 2802.

With particular reference to FIGS. 13 and 14, the plurality of windows 2802 may include different opacity. For example, the windows 2802 a, 2802 b, 2802 c, 2802 d may include opacity of 100%, 75%, 50%, and 25%, respectively. In this manner, brightness or intensity of the light sources 2702 may be adjustable by the clinician. With particular reference to FIGS. 14-16, for example, the windows 2802 may have repeating sequences of the opacity. It is contemplated that the circumferential spacing of the light sources 2702 (FIG. 5) and the repeating sequences of the opacity of the windows 2802 are such that when a light source 2702 is in registration with a window 2802 of a particular opacity, the other light sources 2702 are also in registration with the windows 2802 of the same opacity. With particular reference to FIG. 15, the protruding lip 2708 of the lighting assembly 2700 may include a slot 2706 configured to receive a finger 2810 (FIG. 14) of the window assembly 2800 to rotatably support the window assembly 2800 thereon. Alternatively, the window assembly 2800 may be threadably coupled to the lighting assembly 2700. In either configuration, the clinician may rotate the window assembly 2800 to selectively adjust the opacity of the windows 2802 for desired brightness or intensity of lighting by the light sources 2702.

With reference now to FIGS. 17-19, there is illustrated a window assembly 3800 for use with the tissue dissector 2100 (FIG. 11) in accordance with an embodiment of the present disclosure. In the interest of brevity, portions of the window assembly 3800 substantially identical to the portions of the window assembly 2800 will not be described herein to avoid obscuring the present disclosure in unnecessary detail. The dissector head portion 3200 may include an opacity adjustment indicator 3900 to selectively adjust and visualize the opacity setting of the window assembly 3800. In particular, the window assembly 3800 includes an indicator 3850 that points to the indicia 3860 indicating current opacity setting when the indicator 3850 is selectively aligned with the indicia 3860. In this manner, the clinician can selectively choose registration of the plurality of light sources 2702 with the windows 2802 a, 2802 b, 2802 c, 2802 d of desired opacity. In addition, the dissector head portion 3200 may further include a pair of stops 3870 to limit rotation of the window assembly 2800 between the stops 3870. In particular, the stops 3870 are spaced apart such that rotation of the window assembly 3800 effects different opacity as discussed hereinabove such as, e.g., 100%, 75%, 50%, and 25%. Under such a configuration, the repeating sequences of the opacity of the windows 2802 are such that when a light source 2702 is in registration with a window 2802 of a particular opacity, the other light sources 2702 are also in registration with the windows 2802 of the same opacity. In addition, the dissector head portion 3200 and the indicator 3850 may include mating features. For example, the dissector head portion 3200 may define discrete grooves 3875 to engage the indicator 3850 to improve alignment of the light sources 2702 with the respective windows 2802. It is further contemplated that each groove 3875 may include ramp portions 3875a to facilitate slidable engagement of the indicator 3850 having, e.g., a complementary profile, to that of the groove 3875.

In this manner, the clinician may rotate the window assembly 3800 to selectively adjust the opacity of the windows 2802 for desired brightness or intensity of lighting by the light sources 2702.

The use and operation of the tissue dissector 2100 is substantially identical to those described hereinabove with respect to the tissue dissectors 100, 1100, and thus, will not be described herein.

It is contemplated that the tissue dissectors 100, 1100, 2100 may be used in conjunction with an access device, e.g., retractor, access port, or wound protector (not shown). For example, the frusto-conical shape of the blade member 220 may facilitate insertion partially into the wound protector. It is further contemplated that the battery pack 500 may be removably supported in the handle portion 400 of the tissue dissector 100, 1100, 2100. In addition, the tissue dissectors 100, 1100, 2100 may further include a printed circuit board 700 (FIG. 3) or other suitable control unit including a suitable microprocessor to control actuation of the motor 420 and supply of power from the battery pack 500. For example, the microprocessor of the printed circuit board 700 may monitor power consumption, e.g., current draw, by the motor 420 (which is indicative of torque output by the motor 420) and adjust the power supplied to the motor 420 accordingly to prevent damage or harm in the event aperture 201 is overfilled with tissue and/or tough tissue is encountered. Other safety features may likewise be implemented via the microprocessor of the printed circuit board 700 as cutting optimization features.

As an alternative to the handle portion 400 (FIG. 1) configured for manual grasping and manipulation during use, the tissue dissectors 100, 1100, 2100 may alternatively be configured for use with a robotic surgical system wherein the dissector head portion 200, 3200 are configured to engage a robotic arm of the robotic surgical system in a similar manner as detailed above with respect to engagement of the dissector head portion 200, 3200 with the handle portion 400. The robotic surgical system may employ various robotic elements to assist the surgeon and allow remote operation (or partial remote operation). More specifically, various robotic arms, gears, cams, pulleys, electric and mechanical motors, etc. may be employed for this purpose and may be designed with the robotic surgical system to assist the surgeon during the course of an operation or treatment. The robotic surgical system may include remotely steerable systems, automatically flexible surgical systems, remotely flexible surgical systems, remotely articulating surgical systems, wireless surgical systems, modular or selectively configurable remotely operated surgical systems, etc.

The robotic surgical system may be employed with one or more consoles that are next to the operating theater or located in a remote location. In this instance, one team of surgeons or nurses may prep the patient for surgery and configure the robotic surgical system with the surgical device disclosed herein while another surgeon (or group of surgeons) remotely control the surgical device via the robotic surgical system. As can be appreciated, a highly skilled surgeon may perform multiple operations in multiple locations without leaving his/her remote console which can be both economically advantageous and a benefit to the patient or a series of patients.

The robotic arms of the robotic surgical system are typically coupled to a pair of master handles by a controller. The handles can be moved by the surgeon to produce a corresponding movement of the working ends of any type of surgical instrument (e.g., end effectors, graspers, knifes, scissors, cameras, fluid delivery devices, etc.) which may complement the use of the tissue resecting devices described herein. The movement of the master handles may be scaled so that the working ends have a corresponding movement that is different, smaller or larger, than the movement performed by the operating hands of the surgeon. The scale factor or gearing ratio may be adjustable so that the operator can control the resolution of the working ends of the surgical instrument(s).

While several embodiments of the disclosure have been shown in the drawings, it is not intended that the disclosure be limited thereto, as it is intended that the disclosure be as broad in scope as the art will allow and that the specification be read likewise. Therefore, the above description should not be construed as limiting, but merely as examples of particular embodiments. Those skilled in the art will envision other modifications within the scope and spirit of the claims appended hereto.

Although the foregoing disclosure has been described in some detail by way of illustration and example, for purposes of clarity or understanding, it will be obvious that certain changes and modifications may be practiced within the scope of the appended claims. 

What is claimed is:
 1. A tissue dissector comprising: a handle assembly including an actuator; a head portion including a blade member defining an aperture configured to receive tissue therethrough, the blade member operatively coupled with the actuator for rotation about the aperture; and a lighting assembly configured to provide lighting to the aperture of the blade member.
 2. The tissue dissector according to claim 1, wherein the handle assembly further includes a removable battery pack to supply power to the actuator or the lighting assembly.
 3. The tissue dissector according to claim 1, wherein the aperture of the blade member is tapered along a longitudinal axis thereof.
 4. The tissue dissector according to claim 1, wherein the blade member includes an edge portion configured to cut tissue.
 5. The tissue dissector according to claim 1, wherein the lighting assembly includes a plurality of light emitting diodes circumferentially arranged about the aperture of the blade member.
 6. The tissue dissector according to claim 1, wherein the head portion includes first and second sides opposing each other, the blade member extending from the first side.
 7. The tissue dissector according to claim 6, wherein the lighting assembly is disposed on the second side of the head portion.
 8. A tissue dissector comprising: a handle assembly including an actuator; a head portion including a blade member defining an aperture configured to receive tissue therethrough, the blade member operatively coupled with the actuator for rotation about the aperture to cut tissue; and a lighting assembly including: a circular rim disposed on the head portion and having a light source disposed on the circular rim; and a window assembly rotatably supported on the circular rim, the window assembly including a first window having a first opacity, the first window in registration with the light source.
 9. The tissue dissector according to claim 8, wherein the window assembly further includes a second window having a second opacity different from the first opacity.
 10. The tissue dissector according to claim 8, wherein the window assembly is removably attached to the circular rim.
 11. The tissue dissector according to claim 8, wherein the circular rim supports a plurality of light sources, and the window assembly includes a plurality of windows, at least two windows of the plurality of windows having a different opacity.
 12. The tissue dissector according to claim 11, wherein the plurality of windows include opacities of 100%, 75%, 50%, and 25%.
 13. The tissue dissector according to claim 12, wherein the plurality of windows is arranged in a repeating sequence of opacity such that the plurality of light sources is in registration with the plurality of windows having the same opacity.
 14. The tissue dissector according to claim 11, wherein the head portion includes indicia indicating different opacity and the window assembly includes an indicator selectively positionable on the indicia to selectively align the light sources to the windows having a predetermined opacity.
 15. The tissue dissector according to claim 14, wherein the head portion further includes a pair of stops to limit rotation of the window assembly such that the light sources are in registration with the windows having the same opacity.
 16. The tissue dissector according to claim 12, wherein a longitudinal axis defined by the aperture of the blade member is substantially orthogonal to a longitudinal axis defined by the handle assembly.
 17. The tissue dissector according to claim 14, wherein the head portion and the indicator include mating configurations for alignment of the indicator and the indicia.
 18. The tissue dissector according to claim 8, wherein the lighting assembly includes a plurality of light sources, at least first and second light sources of the plurality of light sources diametrically opposing each other. 